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Learning how to build Lotus Seven replicas...together!
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PostPosted: January 17, 2018, 7:46 pm 
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Location: Gainesville, Mo.
GonzoRacer wrote:
Is it pronounced "EYE-Gor"???


Of course! Just like "It's Frahnk-en-steen!" he screamed in his best Gene Wilder impression! :rofl:

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PostPosted: January 17, 2018, 9:44 pm 
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Joined: March 10, 2006, 12:48 am
Posts: 294
Location: CT
RichardSIA wrote:
Ah, you are going for wide wheels!
Any chance I can get the Cosmic's from you?
Would go great on one of my Spitfires, or maybe another Europa when my fortunes improve.

Sure. Give me a few weeks/months to get the front suspension squared away.


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PostPosted: January 21, 2018, 7:34 pm 
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Joined: March 10, 2006, 12:48 am
Posts: 294
Location: CT
Still getting caught up on the build log - so strap in for another couple rapid fire updates.

Progress has been made, but naturally not as fast as I'd hoped.

Built some motor mounts using poly control arm bushings. Happy with how they came out, short of some of the welds since I was getting impatient.
Attachment:
IMG_20171213_115629985.jpg

Attachment:
IMG_20180107_172707145.jpg

Attachment:
IMG_20180107_172656442.jpg


Next up, I modified the Miata knuckles to convert the lower bolt to 1/2" (drilled the lower holes out to 5/8", then welded in a 5/8" OD, 1/2" ID tube. The upper mount was also sleeved to take a 1/2" bolt. I didn't take any pictures since it wasn't terribly interesting.

With the uprights good to go, I built a control arm jig and tacked up 1 lower control arms. Undeterred by the limited sweep of the tube notcher, I busted out a ghetto setup I made when building the 7. Works well and it looks like I'm not the only one with this idea.
Attachment:
IMG_20171227_105624546.jpg


The rest of the arms are all straight links, so no more jigs should be necessary. To allow for fine toe adjustment, I made a concentric sleeve that can spin in the control arm, and locks down using the rod end lock nut.

Rear suspension mock up started.
Attachment:
IMG_20180107_172621764.jpg

Ignore the ugly bracket on the lower mount - that's getting rebuilt.
Attachment:
IMG_20180107_172644083.jpg


This is when things get interesting and frustrating. Before I commit too much to the suspension design/track width/motor mounts, I need to ensure I can figure out an affordable and strong axle solution. More to come.


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PostPosted: January 21, 2018, 7:39 pm 
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Joined: March 10, 2006, 12:48 am
Posts: 294
Location: CT
Axles. Ugh. My original plan was to press out the Miata hubs and press in mk2 VW guys. The VW hub OD is the same as the Miata, and the axial lengths are within 3mm. Also, perhaps, I'd get lucky and find something that'd match up with the funky Passat 6x114mm bolt pattern. With the a control arm tacked together and the motor mounts in, I started measuring up for axles. The Passat axle outputs from the Passat transmission are shifted towards the driver's side. I thought the motor was pretty centered in the chassis, but the driver's side axle needs to be about 2" shorter than the passenger.

So, what do we know:
  • VW hub presses into Miata knuckle. I got my hands on a VW axle for test fitting - no way that is going to work.
  • Passat axle bolt pattern is strange 6x114.
  • 94 Miata has a flanged axle that does not match the Passat bolt pattern. I believe it's 4x110.
  • This is the same transmission as a Boxster, right?

The last statement - not 100% true. From my research, the Boxster uses a "108mm" Porsche CV, but this refers to the CV OD, not the bolt pattern. Bolt pattern is really 6x94mm. I started going down the rabbit hole of: How do I make use of the custom VW/Porsche axle shafts, Porsche 930 CVs, and somehow mate that to the Miata upright. A week or two later, still no solid plan despite hours of internet wrangling.

Here's what I think i want to do. Adapt the 6x114mm Passat pattern to 4x110 Miata. Laying this out in CAD shows that there really isn't enough ?room for bolt heads on the Passat side of the adapter, and there's only about .180" clearance on the backside of the Passat CV flange, so bolting in the adapter from the inboard side of the CV flange isn't an option. I can weld and redrill 2 of the holes in the Passat flange to match the Miata. A stock '94 Miata axle looks like it'll work perfectly on the passenger side. I just need something that's 2" shorter on the driver side. I really should measure the flange to flange width of the Passat and my Miata diff.

Anyways, here's where this GRM braintrust showed it's value. While researching cutting CV splines, I stumbled on this thread:
https://grassrootsmotorsports.com/forum/grm/cv-axle-splines/62851/page1/

Which brought me to this goldmine: http://interparts.com/index.htm
Using their catalog, I found the interchangeability of the Miata outer CV
Attachment:
miata cv.jpg


I knew about the outer 26 tooth spline, but not the inner 22 tooth. Fortunately, they have an application list for CV axles with the spline count. Unfortunately, they don't list a Miata axle. Luckily, I happen to have a couple around the shop with the wrong inner CV for me. A couple minutes later, I've harvested an axle shaft.
Attachment:
IMG_20180107_172907135.jpg

OK, so I'm now looking for a Mazda family, 22 spline at both end, axle shaft that's somewhere around 17" long. Well, what do you know:
Attachment:
axle shaft.jpg


MX3, Protege, Sephia as listed ought to do the trick. These also have the same outer CV as the Miata.

The final plan for the driver's side axle (final until I get all the pieces and figure out it doesn't work):

  • Devise some sort of VW to Miata adapter
  • Pass'r side: stock '94 Miata axle
  • Driver side: Short Protege axle with outer CV, swap the inner CV for a flanged Miata unit.

That's where I am. I think I have a plan. It seems solid enough. I'll order up an axle this week and see if it does the trick. I have a few hair brained ideas for backup plans - but I'm trying to avoid welding axles as much as possible.


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PostPosted: January 21, 2018, 7:49 pm 
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Joined: March 10, 2006, 12:48 am
Posts: 294
Location: CT
Got a pair of SunTrack axles. One '94 Miata. One Kia Sephia per the plan. The inner CV on both of them is different from the old Miata one I dissected last week. No pictures because I got pretty greasy during the operation. Popped the Kia inner CV off the shaft, popped the Miata one off, took a deep breath, aligned up the splines and.... SUCCESS!!

So, now I have the axles figured out. If I ever need to replace the driver's side, I need to get a couple axles and combine, but the total cost is still <$100, so I'm not too upset. Plus side - if I ever lunch the passenger side outer CV, I have a brand new spare in a box.

Attachment:
IMG_20180113_133533340.jpg


With reinvigorated confidence, I welded up the other lower control arm and called it a day. Hopefully I'll get a few hours in the shop tomorrow to make the rest of the arms. Roller? I probably shouldn't get ahead of myself.

A couple of notes, in hindsight
  • I didn't mark the orientation of the inner tripod when I took it apart. I will need to open it back up and compare against the front to ensure it's all aligned up correctly. If you open up a CV for some frankenstein action, mark the orientation...
  • The discarded Sephia inner CV doesn't fit on the stock Miata axles - so SunTrack must have a different spline diameter vs OEM. I may have lucked out that these two happened to share the same spline, but mixing axles from different manufactures may lead to results different from advertised...


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PostPosted: January 21, 2018, 7:54 pm 
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Joined: March 10, 2006, 12:48 am
Posts: 294
Location: CT
Passenger side is suspended!
Attachment:
IMG_20180114_155848933.jpg

Attachment:
IMG_20180114_155857578.jpg


The design is a bit confusing, and I think it could be simplified. But, this will certainly work. Try as I might, I didn't leave room enough for a conventionally mounted shock, so I'll make up some rockers and move the shocks inboard.

With the suspension worked out, I've started thinking about other modifications that need to get worked out prior to dropping the body back on. One such modification is the brake master cylinder. I'm converting to dual masters and just found someone who did something pretty similar to what I've been mulling over.

Stock design: The brake pedal moves a linkage that connects to a bellcrank that then connects to the master.
Image
Imitation is the highest form of flattery - stolen from a neat build from a guy in Phoenix who's dropping a 2GR into his car. http://www.lotuseuropa.org/LotusForum/index.php?topic=1035.0
Image
Image

This looks like it'll fit in the stock location without needing much modification to the chassis. Once the suspension is done, I'll turn the chassis around in the garage and start work on the master setup. I scored a bunch of master cylinders and balance bars at a fall swap meet.


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PostPosted: January 21, 2018, 7:56 pm 
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Joined: March 10, 2006, 12:48 am
Posts: 294
Location: CT
And finally, we're at the current state.
Weekend Update: Roller status achieved.
Attachment:
IMG_20180121_160344658.jpg


I'm saving cleaning up all the chassis surface rust for the spring. It's a little chilly in CT this time of year, and I'd rather not cover my garage with the dust. There's plenty of work to do in the meantime. Next up is to set up the brake and clutch master cylinders. Then (hopefully next weekend), drop the body on so I can start figuring out the exhaust and rear suspension rocker setup.

Oh, I also weighed it. Because, why not? I'm a little bummed with the results.

829 lbs with the full drivetrain minus exhaust and intercooler. Suspension complete minus shocks. I think the body is fairly heavy at 300-400 lbs minus seats. That'd get me up to 1230 lbs. Add in a battery, intercooler, exhaust , a real fuel cell, some light aluminum seats and it's probably getting to 1450 before the cage. The weight distribution is going to get interesting since front of the body is certainly heavier than the rear, but there's more stuff I need to fit in the back.
Attachment:
IMG_20180120_183859178.jpg


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PostPosted: January 4, 2019, 10:37 pm 
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Joined: March 10, 2006, 12:48 am
Posts: 294
Location: CT
I've been slowly plugging away for the past year. To summarize: I ran into a bit of a hurdle when the shocks didn't fit as well as I'd hoped. Took some staring at it, a couple failed starts, then finally settled on the inboard suspension arrangement below. With the car holding up its own weight, I cobbled the shifter together from some Boxster and Neon parts. And the latest update is to tack up the exhaust.

Image
Image
Image
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PostPosted: January 4, 2019, 11:18 pm 
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Joined: January 13, 2008, 9:07 pm
Posts: 1390
Location: Glendale AZ
Love it ! Keep up the great work !

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